The package tray needs to come out in order to replace the speaker covers or speakers.
1. Remove the 3 bolts attaching the deck to the frame
2. Remove the side panels that hold down the deck so you really have to take these off. They should just snap off.
3. Remove the high mounted stop light.
4. Either remove the back seats or try to fold the back seats down and see if that gives you enough room.
5. To remove the deck you first need to go in through your trunk and you'll see 4 white clips. Push these up with some pliers, then from the inside just tug it away. Be careful shimmying the tray out, since you do not want to break it.
6. Remove old speakers. They should be held down by 3 screws.